Evaluation of UASB/CO2 stripping system for simultaneous removal of organics and calcium in linerboard wastewater



A combined upflow anaerobic sludge blanket (UASB) and CO2-stripping system was evaluated for its capacity to simultaneously remove organic compounds and calcium from linerboard mill wastewater. A continuous-flow UASB has significant potential to remove organic compounds, and its removal efficiency is closely related to volumetric organic loading. After the UASB process, a gradual decrease of pH was observed and CO2-stripping indicated the formation of acid/methane and carbonate. The high concentration of carbonate that was generated from the elevated pH of the CO2 stripper easily reacted with calcium in the wastewater to form a solid-phase calcium carbonate. The significant amount of methane that was produced during the UASB process implies that methane-producing bacteria dominate the microbial composition of the reactor. In the CO2 stripper system, calcium removal and alkalinity consumption rose simultaneously with increasing solution pHs. This result suggests that the combined activity of the UASB reactor and the CO2 stripper system is a powerful tool for removing organic compounds and calcium from linerboard wastewater. Such a system would allow water from the linerboard production process to be reused and be discharged with fewer toxic compounds. © 2010 American Institute of Chemical Engineers Environ Prog, 2011